Remove docs on 'using', which only describe the no longer necessary...

Remove docs on 'using', which only describe the no longer necessary bootstrapping technique. Ref #336.

docs/index.txt

@@ -19,7 +19,6 @@ Documentation content:
    history
    roadmap
    python3
-   using
    setuptools
    easy_install
    pkg_resources

docs/using.txt

-================================
-Using Setuptools in your project
-================================
-
-To use Setuptools in your project, the recommended way is to ship
-`ez_setup.py` alongside your `setup.py` script and call
-it at the very beginning of `setup.py` like this::
-
-    from ez_setup import use_setuptools
-    use_setuptools()
-
-More info on `ez_setup.py` can be found at `the project home page
-<https://pypy.python.org/pypi/setuptools>`_.